One day about five years ago, Frank Nolwo, a compact, quietly spoken boat skipper from the upper reaches of the Sepik river, in northern Papua New Guinea, woke up and headed into town. Nolwo, who is 42, has nine children. He was adding an extension to his house, and needed to buy some building materials.

You do not just pop to the shops if you live in the upper Sepik. Nolwo left Kagiru, his village, in the early morning. Like other isolated clutches of palm-roofed houses on the river, Kagiru has no electricity, no mobile phone signal, and no road connecting it to anywhere else. Even by Papua New Guinean standards, the region is regarded as hot, poor and difficult to live in. When it rains, the place floods. When there is a drought, the creeks and streams dry up, stranding people and their canoes. It takes days to walk anywhere. For powerful, almost unarguable, geographic reasons, life in the upper Sepik has resisted meaningful economic development for thousands of years. There are lots, and lots, of crocodiles.

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After a day on the water, Nolwo reached Ambunti, a large village of around 2,000 people, where he spent the night. The next morning, he motored on. Nolwo was a prosperous and influential local figure. As well as running his boat, he was the chairman of a district of more than 30 small villages that included Kagiru. Even so, the trip was a major undertaking. The fuel alone was going to cost around £200. At around lunchtime on the second day, Nolwo moored his boat and got on a truck bound for Wewak, the provincial capital and his destination, a four-hour drive away on the coast. It was at the market in Wewak, buying hardware, that Nolwo ran into another district chairman from the upper Sepik, named David Salio, who invited him to a meeting in a local hotel about carbon trading.

The In Wewak Boutique hotel is the smartest place in town. Set on a bluff just outside the centre it is a white, two-storey building with a small swimming pool and verandas that look out over the South Pacific. The meeting that night was organised by Stephen Hooper, a former Aussie rules football player and entrepreneur. A huge, broad man with a background in mining, Hooper had been working on and off in Papua New Guinea since 2007, first on a timber project, and then on schemes to sell carbon credits derived from forests.

Nolwo sat and listened. He had been to high school and remembered the idea of photosynthesis, so what Hooper was saying about leaves and carbon and oxygen was not completely bizarre, but it was pretty far out. The gist was this: because of pollution in countries far away, and something happening to the atmosphere, people along the Sepik river were going to be able to start selling the clean air produced by their trees. And by the sound of things, they might get very rich.

“It was surprising to me,” Nolwo told me recently. “It was something I hadn’t ever heard before. Like, I can catch fish and sell them for money. But this one was totally different.” He was intrigued. Four other local chairmen had already signed up with their communities. Nolwo decided to think about it. He bought what he needed for his house and started the long journey back to Kagiru.

Back on the water, Nolwo looked at the skinny, grey-barked trees set back from the muddy banks, thickening into forests on the hills behind. They framed the powerful and unforgiving landscape that he had known all his life: sources of food and fuel and spiritual energy, where men and women would spend a few days on their own from time to time, to prepare for rituals, and to come of age. Now he found himself considering the trees in a new light. Nolwo’s mind filled not only with financial possibilities, but with the chance to contribute to a project of global importance. “This is to save the life of the world,” he thought. When he got home, Nolwo explained the whole idea to his wife.

Beautiful, in theory

The first time you hear about REDD+, it tends to make a big impression. The acronym stands for Reducing Emissions from Deforestation and Degradation. It is the UN’s plan to bring forests into the fight against climate change: to measure their contribution to stabilising the atmosphere, and to pay for it.

REDD+ is, among many other things, a beautiful idea. There are three trillion trees on Earth and they are perfectly made to take carbon dioxide out of the atmosphere. Every year, the world’s forests and bogs are thought to absorb around 1.6 gigatonnes of our 10 gigatonnes of manmade emissions. Of course we are degrading these ecosystems at a terrible rate. Practices such as cutting down trees, draining swamps and burning brush, all to make way for agriculture, produce anything between 10% and 20% of greenhouse gas emissions in their own right. In an era of climate change, destroying forests is one of the most harmful things we can do. It takes one of our best hopes of controlling the damage and sets it against us. It is what is known in the pidgin of Papua New Guinea as a “double buggerup”.

There are three trillion trees on earth and they are perfectly made to take carbon dioxide out of the atmosphere

REDD+ promises to turn the situation around. Given how valuable these biological systems are – forests are “carbon capture and storage” technology in a cheap yet wondrous form – the idea is that we should pay for what they do. Where intact wildernesses remain in developing countries, scientists should figure out how much carbon they soak up and store, and governments and communities should be incentivised to preserve them rather than turn them over to asphalt or industrial farming. On our battered, warming planet, a tree should be worth as much standing as felled.

The mechanics of how to do this are complicated, no doubt, but when you think about it, not beyond the capabilities of 21st-century science and bureaucrats: satellites and ground inventories to monitor deforestation, carbon markets, offset payments, and international aid to channel money from richer, polluting countries to poorer, tree-protecting ones. A vision of this future has entranced UN climate change talks since REDD was first proposed in 2005. At a cost of around $6m each, 51 countries, from Ethiopia to Ecuador, have spent the last five years preparing for the programme. Some $7bn has been pledged to get the system up and running, and REDD+ is one of the elements that negotiators are pushing to include in the grand treaty that the world is seeking at the Paris climate change summit, which starts next week.

If the whole thing works as it is supposed to, the benefits would be remarkable. Carbon emissions would go down and forests would be saved – the same forests that shelter 77% of the world’s threatened bird species, supply water to a third of the world’s large cities, and are home to 60 million indigenous people, among the most vulnerable communities on Earth. Money would flow from north and south and new kinds of forest economies, based on living things and biodiversity, rather than denuded landscapes, would arise. Sociologists sometimes call climate change a “wicked problem” because of all the noxious, mutually reinforcing elements that go into it. On paper, REDD+ sometimes has the appearance of a wicked solution for all the good that it might do.

And that is its weakness too. Some theories just do not work in practice, and almost from its inception, REDD+ has been criticised as impractical, financially unsound and a diversion from mankind’s number-one priority of curbing our consumption of fossil fuels. In some quarters, the scheme represents everything that is wrong about the UN approach to tackling climate change: theoretical, multilateral, unwieldy, rather than something that might actually have a bearing on the nitty‑gritty, day-to-day skirmishes over land and resources that are quickly putting the health of the planet beyond reach.

“It is bonkers,” Chris Lang, a blogger who has covered the programme since 2008, told me, “on so many levels.” The question is whether that is precisely what genuine solutions to climate change are going to look like. No one ever said it was going to be easy.

The birth of REDD

One of the most bonkers things about REDD+ has always been that it was dreamed up in Papua New Guinea. In Wewak, in fact. Not on the day that Frank Nolwo came to town, but years earlier, in the spring of 2003. One afternoon, the former prime minister, and father of the country’s independence, Grand Chief Sir Michael Somare, was walking along the town’s beach with a charismatic business student called Kevin Conrad.

Conrad was in his mid-30s. The son of American missionaries, he had grown up near the village of Hayfield in the Sepik – he was born under a tree, he liked to say – and had known Somare since he was a boy. After graduating from high school, Conrad had gone to study in California, working at Nasa’s jet propulsion laboratory in Pasadena and investment banks before taking a job with Angco, Papua New Guinea’s largest coffee exporter. Now he was studying for an MBA in London and New York, and working informally as an adviser to Somare.

That day, the grand chief had forests on his mind. The country has the world’s third-largest rainforest, after the Congo and the Amazon. It is a kind of pleasure-dome of biological diversity: the haunt of 19,000 known plant species, tree kangaroos and the cassowary, a 6ft-tall flightless bird. But its trees are commercially valuable too, and for decades the country has been home to a notoriously corrupt logging industry. In 1987, a national commission described timber companies “roaming the countryside with the self-assurance of robber barons; bribing politicians and leaders, creating social disharmony and ignoring laws”.

Sixteen years later, a follow-up report had concluded that “the robber barons are now as active as they ever were”, and Somare was under pressure from the international community to do something. Estimating that 70% of Papua New Guinea’s timber exports were produced illegally in some way, the World Bank offered the nation a one-time loan of $17m to suspend its logging industry altogether. But that was nowhere near the royalties that the government received every year – which were closer to $50m – and which Somare viewed as essential to the development of the country.

On the beach in Wewak, Somare put the problem to his young adviser. “Sir Michael said, ‘Actually I agree with what the World Bank is offering in principle,’” Conrad recalled. But Papua New Guinea could not afford to give up logging on those terms. The country is poor. People get by on average earnings of about £4 a day. Somare challenged Conrad to come up with an alternative way to make money from its forests.

Conrad spent two years working out his answer. He had no background in deforestation or climate science or economic development, but he was a quick study. He read about “payments for ecosystem services” – an idea that had been trialled in Costa Rica to reward landowners for maintaining healthy waterways, or bird habitats. He learned about carbon markets, in which companies support pollution-preventing schemes on international exchanges in order to offset their emissions. Conrad pondered the astonishing quantity of carbon that must be stored in Papua New Guinea’s forests, which cover 370,000 square kilometres, an area comfortably larger than Italy. He pored over the dense, forbidding texts of the UNFCCC, the UN’s mammoth climate change negotiating process, and he came up with an idea: could a country such as Papua New Guinea be paid to keep its forests intact? Could it sell, as carbon credits, the millions upon millions of tonnes of emissions that would be saved if it did not cut down its trees?

Conrad was interested in money. He was determined to upend conventional thinking about aid and conservation. Growing up in the Sepik, he had seen foreign NGOs come with vague ideas about preserving the wilderness and no money for the communities that lived there. “It frustrated me,” he said. “It seemed to me they were asking them to continue to be poor, even though they had a world-class asset.” In November 2005, with Somare’s blessing, and the support of Costa Rica, Conrad submitted an 11-page proposal to the UN’s climate change summit, which had gathered in Montreal.

Kevin Conrad, who grew up in the Sepik, devised the REDD idea Photograph: Jonathan Saunders

The timing, and the character, of Conrad’s idea could not have been more potent. Calculating the financial implications of climate change, and devising market-based mechanisms to address the problem, was precisely where the smart thinking was at. In 2006, the Stern Review on the Economics of Climate Change identified tackling deforestation as a “highly cost-effective way” to curb greenhouse gas emissions. Soon after, REDD got its acronym, and began to gain traction in the UNFCCC. The World Bank got involved. In 2008, a British government review into the future of the world’s forests, conducted by Johan Eliasch, a Swedish businessman and environmentalist, predicted that a well-designed REDD system could cut global deforestation by up to 75% by 2030.

There was a political edge to REDD, as well, that made it stand out in the schismed world of the climate change talks. The main reason why the UNFCCC has been stuck all these years is because the world’s developing countries accuse industrialised nations of wrecking the planet, and they want hundreds of billions of dollars in compensation. The rich countries, for their part, observe that almost two-thirds of greenhouse gasses now come from the developing world, and that they are not going to make any deep cuts, and certainly not part with any money, until everyone agrees to reduce their emissions.

REDD ignored this standoff. From day one, the idea was that poor countries such as Papua New Guinea would be happy to curb their emissions by preserving their forests in return for money. (Around 70% of Papua New Guinea’s carbon emissions come from logging.) “That was game-changing,” Conrad said. The commercial straightforwardness of REDD threatened the deadlock that suited major players at the talks. “The US didn’t want it. The US wanted the status quo, which was that they wanted to do nothing.”

Conrad himself personified the dynamic, ideologically versatile, nature of what he was proposing. He was hard to pin down, exactly: based in New York, but representing Papua New Guinea; good looking, comfortable in the spotlight, fluent in the language of markets and technology and “paradigm shifts”, while able to tell stories of his humble childhood in the Sepik. In 2007, he made news around the world when he shamed the Bush administration for blocking progress at the final plenary session of the Bali climate change summit. “If you’re not willing to lead,” said Conrad, addressing thousands of delegates, “then get out of the way.” The sight of tiny Papua New Guinea facing down the United States made him something of a hero at the negotiations.

I first met Conrad around this time. It was during a week of tense, soporific talks in Bonn in the run-up to the disastrous Copenhagen summit of 2009, and he stuck out a mile. He was like a Hollywood actor playing the part of UN climate change negotiator. He talked about how the sea had risen to submerge a tree in Wewak, where he used to make out with his girlfriend, and boasted about how he and his allies – by this point Conrad was leading a group known as the Coalition for Rainforest Nations – were running circles around their enemies at the talks. “That’s because we actually know how to get something done,” he said. In the wreckage of Copenhagen, REDD was one of the few elements of the UN process to emerge with its momentum intact. In 2010, Norway and Indonesia signed the world’s first major REDD deal. It was worth $1bn.

The carbon craze

Back in Papua New Guinea, however, things had not gone exactly to plan. Since the first visits of white traders in the 19th century, and a fevered gold rush in the 1930s, the sheer difficulty of the country – its ravines, jungles, and history of cannibalism – has acted as a magnet to adventurers and unlikely schemes. It is as if the country’s somewhat virgin, somewhat violent quality is a guarantee that riches must lie there somewhere, and between 2008 and 2009 as many as 90 foreign “carbon developers” descended, determined to unlock the value waiting in its trees.

The international publicity courted by Somare and Conrad created a demand that Papua New Guinea could not meet. An Office of Climate Change & Carbon Trade was set up and promptly overwhelmed by proposals for REDD schemes that it had no way to administer. The idea existed on paper, that was all. On flights to the capital, Port Moresby, Conrad would find himself surrounded. “I would have six or seven different groups come to me on the plane, pitching me,” he said.

Out in the bush, encounters between the carbon developers and forest clans took on an ugly, exploitative aspect. Papua New Guinea’s constitution gives communities strong land rights, but around a third of the population is illiterate. Fanciful notions of the carbon craze caught on among many Papua New Guineans, who had no way to conceptualise the trading of a gas said to be stored in their trees. People talked of huge ships, with great bulbous tanks, lining up along the coast to suck the air from the forests inland. Markets started selling plastic bags, to go and collect carbon. Villagers spoke of “sky money” and worried that Papua New Guinea might run out of oxygen. In early 2009, the director of the new climate change department, a schoolfriend of Conrad’s named Theo Yasause, was suspended for allegedly printing his own carbon credits. He was later imprisoned for shooting a man outside a nightclub. “The mood got out of control,” Conrad admitted.

Papua New Guinea was not the only place where early REDD experiments went wrong. In the Amazon, there were reports of “carbon cowboys” displacing communities from ancestral lands to make way for schemes being paid for by powerful corporations to offset their emissions. In southern Brazil, for example, villagers living next to the Guaraqueçaba Climate Action Project – an $18m scheme funded by General Motors, Chevron and American Electric Power – found themselves blocked from hunting, fishing or tending their forest gardens by local environmental police, known as the Green Force.

NGOs and governments reported these horror stories to the UN climate talks. Forest campaigners accustomed to working with indigenous landowners were not surprised. When money and trees mix, it is normally local people who get screwed. To its critics, the early troubles of REDD illustrated two fundamental problems in its design. The first was that Conrad’s central insight was an abstraction. The idea that developing countries should be paid for the emissions that would have been caused if they had cut down their trees was a hypothetical. How do you measure, and price, something that did not happen? The concept was mind-bending enough in international meetings of forests experts, let alone in parts of the world with weak governments, disputed land tenure and uncertain notions of what is going on in their forests in the first place.

When money and trees mix, it is normally local people who get screwed

Second, and more profoundly, REDD came across as a distraction. It was something that sounded impressive, and would involve a huge amount of time, money and effort but it was, essentially, a glorified carbon offset scheme that would allow rich countries to continue to pollute, as long as they could afford to pay poor people not to cut down their trees. “Through REDD you can give the impression that not only are you solving deforestation, you are addressing climate change, without doing the difficult thing of actually leaving fossil fuels in the ground,” said Lang, the blogger. “If we don’t stop climate change, the forests are all going to burn down anyway.”

In December 2010, REDD was rebranded as “REDD+”. It lost its earlier, single-minded focus on reducing emissions and carbon markets and was expanded take a more holistic view of the value of forests and the lives of the people who dwell in them. Activities that could now be funded under the programme came to include “non-carbon benefits” such as “opportunities for wealth creation and wellbeing”.

Conrad found himself increasingly marginalised on the international stage. His earlier dynamism now read as high-handedness and arrogance. And while REDD+ retains his core idea of paying nations to preserve their trees, he resents its gradual diffusion over the years. “It’s all about getting everybody to hold hands in the forest and sing Kumbaya,” he told me. “It has been frustrating.” The carbon craze in Papua New Guinea damaged him too. In 2012, Conrad was fired as the country’s climate change ambassador. Since then, he has been representing Panama in the talks.

At home on the Sepik, Frank Nolwo did not know about any of this. After the meeting in Wewak, he discussed selling carbon with the people of Kagiru, and then more broadly across his district. In 2011, the clans signed up, authorising Hooper, the Australian developer, to sell carbon credits on their behalf. After the chaos of a few years earlier, the government in Papua New Guinea had authorised five official pilot projects in the country, of which Hooper’s planned scheme in the Sepik – known as April Salumei – was the most advanced. With the inclusion of Nolwo’s district, the project came to cover an area of 6,000 square kilometres, an area larger than Norfolk.

A scientist flew in from New Zealand to calculate the amount of carbon in the trees. At first Nolwo thought someone would arrive with containers and take the stuff away. But he soon learned it would just happen on a market somewhere. “I knew that when carbon was traded we would start to receive the money,” he told me. “My understanding was that it would take some time.” He began to wait, and hope.

And that is more or less where the rest of the world has got to with REDD+: waiting, hoping, wondering if this bewitching idea can possibly work. Before I travelled to Papua New Guinea last month to see how the programme is unfolding in the land of its birth, David Nussbaum, the chief executive of WWF in the UK, reminded me of the promise that remains, glinting, in Conrad’s idea. “The prize is that we preserve an indefinite carbon sink, that we help mitigate climate change, that we help secure livelihoods that are constructive and positive for very large numbers of people,” he said. “There is an awful lot of people who stand to win if we can get this right.” On the other hand, there are such things as ideas that are impossible to realise, and they do not help anyone at all.

The appeal of logging

I landed in Port Moresby at dawn on a Friday morning.There was a drift of smoke curling among the iron rooftops of a small settlement across the highway from the guesthouse where I was staying. There had been a fight the night before. A highlander had been shortchanged at the local market, and someone was stabbed with an umbrella. Things had escalated, and a few houses got burned down.

I listened to this, a little stunned and jet-lagged, and found myself staring at a pair of hills rising in the distance. Port Moresby is a scatter of neighbourhoods, rather than a continuous city. Unfinished apartment blocks stand among bare, brown slopes. These are stripped clean of anything that might possibly resemble a tree. That’s because Papua New Guineans consume about 1.8 cubic metres of firewood a year – about the same as Europeans did, before we started burning coal.

One of the easiest things to forget, living in a deforested nation, is that people cut down trees to improve their lives. “To convert millions of acres of wildwood into farmland was unquestionably the greatest achievement of any of our ancestors,” wrote Oliver Rackham in his history of the British countryside in 1986. And he was not talking about the Romans, or the Saxons or the Industrial Revolution. More than half of Britain’s original woodland, stumps and all, was probably gone by 500BC. Wild forests are magnificent, but they are also incompatible with lots of things that human societies like to do. In the 1990s, a Scottish geographer, Alexander Mather, coined the phrase “forest transition” to describe – roughly speaking – how nations cut down their trees, realise they have cut down their trees, and start, eventually, haltingly, to plant trees again.

One of the easiest things to forget, living in a deforested nation, is that people cut down trees to improve their lives

Papua New Guinea has not gone through its forest transition yet. According to the Center for International Forestry Research, it is probably at stage two, known as “frontier conditions”, where things really start to speed up. According to the government, some 15m of its 37m remaining hectares of forest are currently earmarked for timber production. But as of now, all is not lost. Recent satellite data shows that 80% of the country has trees growing on it. From the windows of a plane, the landscape looks, most of the time, as if it has had a chunky, woolly green rug thrown over it.

On a good day, this is what makes the country appear to be the perfect test case for REDD+, and for the UN’s broader vision of “green economies”, in which developing countries manage to avoid the same fossil-fuel burning, tree-cutting path that the rest of us have followed. “If it is going to work anywhere it has to work in Papua New Guinea,” the UN’s resident coordinator, Roy Trivedy, told me. “Papua New Guinea is one of a very, very small number of countries in the world that has a really big choice to make about a development model that is different to the normal one.”

The rest of us have a stake in that decision too, of course. If Papua New Guinea manages to save the largest rainforest in the Pacific, then the planet will benefit. But what sacrifices will it have to make along the way? Some 85% of Papua New Guineans still live in rural areas. Small-scale farming to feed a growing population is one of the major drivers of deforestation. The place is crying out for modern agriculture and decent roads. A big conceptual problem with REDD+ and “green economies” in general is imagining how, exactly, a country can ever become prosperous and industrious if it is constrained from clearing and draining its land. Even environmental activists struggle with this.“When I feel nationalistic, any opportunities to develop – [even] if it means chopping some trees down – you have to do it,” Thomas Paka, the chairman of the Eco-Forestry Forum, the country’s leading umbrella group for forest NGOs, told me.

This historic trade off between deforestation and economic development is REDD+’s biggest obstacle. The international logging industry knows this, and its opposition to the programme has made it an unusual bedfellow – to put it mildly – with forest campaigners who also hate the scheme. Bob Tate, a wiry Australian, runs the Papua New Guinea Forest Industries Association, which represents the country’s Malaysian-controlled timber companies. He warned me about defamation when I turned on my tape recorder and then said: “Kevin Conrad is the biggest con spiv merchant this country has ever seen.” Tate described REDD+ as a “never ending donor project” that would prevent Papua New Guinea from ever realising its economic potential. “All you natives can get back in the bush and live in poverty and we’ll give you a bit of pocket money,” he said. “That is how the UN run it.”

It is hard to exaggerate just how bad the reputation of the logging industry is in Papua New Guinea, and yet it still exercises the hopes of many isolated communities as the only way to obtain a road, a bridge, a school and a smattering of income from royalty payments. Indeed, a central reason why Stephen Hooper was able to launch his REDD+ project in the Sepik river in the first place – and the source of its avoided emissions – was that most of the communities had agreed to have the area logged in 1996. Talking to government officials in Papua New Guinea, I often sensed that they saw a hazy, undesirable connection between deforestation and progress. Logging is ugly, but at least it is real. And there are kickbacks all along the way. Late one afternoon, I ended up at the headquarters of Papua New Guinea’s forest authority, which has 800 officers, short on vehicles and petrol, to monitor the entire country. “Everyone hates the logging companies,” a senior official told me. “But what is the alternative?” He paused. “And besides, our ministers, they like Malaysians.”

The carbon in the trees

This is the development dilemma, more or less, for which Kevin Conrad dreamed up REDD. A decade later, he remains adamant that the only way it will ever work is if carbon schemes can actually put as much money in people’s pockets as raw logs. Well, how much carbon is out there in the trees? And what could it be possibly be worth? Early one morning, I flew to Madang, another town on the country’s northern coast, to find out.

George Weiblen, a botanist from the University of Minnesota, met me at the airport. Weiblen, who is 46, has been studying Papua New Guinea’s trees since he first visited the country as an amazed and terrified graduate student in the early 1990s. He and his research partner, a Czech entomologist named Vojtech Novotny, were besieged by business offers during the carbon craze just over five years ago. They steered clear, and have largely stayed out of the sensitive politics of REDD+ ever since. But they happen to possess some of the most detailed data ever compiled about Papua New Guinea’s trees, including how much carbon they contain.

In 2010, Weiblen and Novotny established a 50-hectare rainforest research plot about 100km west of Madang, as part of a network of international sites administered by the Smithsonian Tropical Research Institute in Panama. Over the next three years, researchers – mostly local villagers – proceeded to count, measure, and record the stem of every tree in the plot more than 1cm wide. They found a total of 288,204 stems and just over 500 tree species inside the 5km x 1km plot – around 10 times the number of tree species native to Britain. “The amount of data was sort of beyond my comprehension,” said Weiblen.

Last month, Weiblen was driving out to inspect the site. Operating in Papua New Guinea means spending a lot of time, and money, worrying about life’s essential components: food, fuel, water, security. (Earlier this year, three men attacked Weiblen’s car with a home-made catapult). We ran errands in Madang for an hour or two, picking up rice, sunscreen and spicy food for camp. At one point we parked up at the town’s main betel nut market, the mild stimulant that is ubiquitous in Papua New Guinea, which was the location of a cholera outbreak a few years ago. I asked Weiblen if many students from Minnesota volunteered to come out and work on his projects. “The ones whose eyes light up,” he said, “I am particularly suspicious of.”

The drive took us out to the west. It wasn’t long before we left the tarmac, and were on sand roads cut since the 1970s by logging companies as they have penetrated deeper and deeper into the forest frontier. Weiblen, a tall, bookish figure who has a habit of cackling suddenly, normally about some mishap or another, told me about a Polish graduate student who nearly fell out of a balloon in a crazy scheme to study the tops of trees. As we neared the research site, we entered an active logging concession and saw stacks of trunks of dull red kwila – Papua New Guinea’s most valuable tropical hardwood – lined up by the side of the road. “That’s the good stuff,” said Weiblen. The timber in a single mature kwila tree is worth around $10,000.

We spent the night in Wanang, the nearest village to the research plot, and continued the journey on foot the following day. Dressed in shorts and the green singlet of one of Papua New Guinea’s rugby league teams, Weiblen walked fast among the roots and draped vines that hung down from the trees above. Since the summer, Papua New Guinea has been experiencing its worst El Niño drought since 1997, and Weiblen was taken aback by the lack of moisture in the air, and the sunlight piercing through the canopy. Dry leaves fell from the sky. “This is just weird,” he said. Every few minutes he would stop to point out one rainforest curiosity or another: the great buttressed trunks of 30-metre high mon trees, or the recent scar of a landslide, covered in a fresh bed of clematis. Huge butterflies floated by. Weiblen stepped over a stream. “We have the oddest leeches,” he said. “They basically feed on your eyes.”

Getting a snapshot of the amount of carbon in the trees, it turns out, is one of the simpler things to measure in a rainforest. All you really need is a respectable sample of tree trunk widths, taken at 130cm from the ground – a measurement known as DBH (diameter at breast height) in the forestry trade. Once you have the DBH, you enter it into an allometric equation, a formula devised by biologists to calculate the size of the rest of a living organism, along with the wood density of each species. In the case of kwila (Intsia bijuga), a mature tree with a girth of around 50cm will have what botanists call an “above ground living biomass” of just under two tonnes. Half of that is deemed to be carbon, which works out at one tonne per tree.

Using the data from the research plot, Weiblen’s team came up with a figure of 105 tonnes of carbon per hectare in Papua New Guinea’s lowland rainforest, closely agreeing – to within 5 tonnes – with other studies. The complicated part, when it comes to REDD+, is extrapolating samples like this over larger areas and time. Research in Wanang has shown that the amount of carbon in the trees can vary from between 50 to 175 tonnes per hectare within the space of a few kilometres – creating an incentive for carbon developers to try and game the figures in their particular stretch of forest. Even less is known about how trees retain and release their carbon over the course of years and decades. Papua New Guinea’s rainforests, for example, are unstable. Because of earthquakes, floods and landslides, their trees have mortality rates twice as high as other parts of the world. While this may increase the biodiversity of the forests, it means that they also hold less carbon. Based on biomass studies, Papua New Guinea’s lowland rainforests might contain as little as half the carbon per hectare of their equivalents in Africa and Asia.

Does that make them less valuable? Less worth saving? One morning, in the research plot with Weiblen, I got tangled up in these questions. On the one hand, the science of measuring the carbon content of trees appeared not very complicated at all. Laborious, but totally achievable. Around me, the trunk of every tree I could see was looped with aluminium wire, with a numbered dogtag hanging from it. On the other hand, monitoring and monetising the actual carbon cycle over time in these places – the fungi were breathing, the leaves were rotting, the trees were breathing, vines were photosynthesising, every conceivable surface was covered in ants, also breathing – seemed almost beyond reason. Because of the drought, the air tasted subtly of smoke. A thousand fires were burning in the forest, releasing untold tonnes of carbon dioxide into the atmosphere. Would someone pay for that?

I tried to interest Weiblen in these matters, but he looked at me, unblinking. “I don’t care,” he said. For people who work, live and research day to day in forests, the abstractions and ambitions of REDD+ can seem terribly remote. (Weiblen, for instance, is busy trying to get his research site formally protected by the provincial government and to raise funding for his next tree census). And that is a problem. How many years will it take to figure this stuff out? Trivedy, the UN resident coordinator, admitted that REDD+ was taking too long to bring to fruition in Papua New Guinea. “I think it’s fair to say there is growing impatience,” he said. Important things are happening: next year the country will begin its first ever national forest inventory. But it will be a decade or more, Trivedy predicted, before the country has a fully working REDD+ system. “The theory is right,” he insisted. “But we’ve got to try and get some quicker benefits to people so they can see, OK, that is the incentive, I’m going to choose to keep my trees.”

The arrival of the lights

One of the difficulties with REDD+ at the moment is convincing people to be patient, and to show faith. In the long run, the vision is that countries will achieve large, official nationwide emissions savings, and they will trade these, most likely on a massive government-to-government basis. In the meantime, however, entrepreneurs and communities who have set up REDD+ pilot projects in the last few years want to sell carbon credits now, on voluntary markets, and to wait for a global architecture to emerge.

In Papua New Guinea any talk of individual schemes raises uneasy memories of the carbon craze. But that has not stopped one man, and one project from going ahead anyway. Stephen Hooper, the Australian carbon developer who established the Sepik river REDD+ project, which Frank Nolwo joined, sold his first carbon credits in 2013. The project, known as April Salumei, has been certified to avoid 23m tonnes of carbon emissions over the next 38 years. At $5 a tonne, the UN’s current notional price for REDD+ transactions, that could work out at $115m.

So far, Hooper has sold around 200,000 tonnes to companies voluntarily offsetting their emissions and received about $300,000 in return. Under his “benefit sharing” agreement with the landowners, Hooper’s company receives 30% of that, while 60% goes to the community and 10% to the national government. The first thing the landowners wanted were boats. Hooper bought five. The next thing the district chairmen asked for was 20,000 Papua New Guinea kina each (about £4,500) to spend on health and education projects in their communities. That disappeared without trace. “We’re not perfect,” Hooper told me.

Frank Nolwo: “I just sit where I am and the money comes,” he said. “It is kind of like a miracle thing happening.” Photograph: Sam Knight

On a recent Tuesday evening, Hooper was back at the In Wewak Boutique hotel giving out mobile phones. The latest sales of the carbon credits from the Sepik have been to Qantas, Australia National Bank and Rema 1000, a supermarket chain in Norway. Hooper wanted people in the five districts involved in the project to take pictures of their daily lives, which he could then share with their customers. “Maybe someone finds a big snake?” Hooper prompted. The chairmen nodded and looked at their phones. Nolwo was not there. He was out in his district, preparing to welcome Hooper and the rest of the chairmen the following day, when one of his villages was due to receive a shipment of solar lights paid for by the project.

Hooper has been pretty much ever present alongside REDD+ in Papua New Guinea. At first he came for the money. By 2010, he had remortgaged his family house outside Perth, sold his car, boat, and the last stock options in Quest Minerals, the mining company he used to run. “It was probably around that time that I realised there was no pot of gold,” he said. Since then, Hooper has become a vaguely controversial figure in Papua New Guinea, simply for refusing to give up. When I was there, Hooper seemed to be everywhere, lobbying ministers, cajoling officials, trying to get a target of 2m hectares for REDD+ projects into the country’s paperwork for the Paris summit. That evening in Wewak, when we sat down for dinner, I asked one of the five chairmen of the April Salumei project, Philip Wablasu, to explain carbon trading to me and he smiled confidentially. “Steve knows,” he said.

The next morning, in the dark, we set off for Binomo, Nolwo’s district. We reached the river at noon and boarded two of the project’s new speedboats. The water in the Sepik was low, because of the drought, and the air – as everywhere – was blurred with the haze of distant fires. “Carbon dioxide,” said Nelson Garabi, one of the chairmen. The solar lights were being delivered to Igai, one of the villages in Binomo which, like all the rest, had no electricity. When we arrived, Nolwo was standing in front of a makeshift arch, fashioned from a palm leaf, next to a handwritten sign that said: “Welcome! Welcome! To the land of ‘untouchable virgin forest’ the land of fresh oxygen (O2) the purifier of green house gases” (sic). A sing-sing – a ceremonial celebration – was under way. The men and women of Igai wore feathers, and had bright turquoise and yellow dots painted on their faces.

Nolwo led the procession up to the centre of Igai, away from the river. According to Papua New Guinean custom, the men gathered in the main village hall, known as a haus, while women, children and teenagers stood or sat on the ground. After five years of hearing about carbon trading, this was the first time that many of them had seen anything arrive as a result. There were speeches. “The forest is your home,” exhorted Anton Pakawi, a former schoolteacher who handles the day-to-day administration of the project. “The forest is your sister. The forest is your brother.” Nolwo said a few words, but spent most of the time looking quietly amazed. “I just sit where I am and the money comes,” he said. “It is kind of like a miracle thing happening.”

Then it was time to turn on the lights. The first four went up in the village church, a skeletal structure that was more of a suggestion than a building. The idea was that children would be able to use the lights to do homework by night for the first time in Igai’s history. It was still early afternoon, though, and at first there was nothing to see. People drifted away. A man climbed a tree to bring down coconuts. But then darkness came, as it does in Papua New Guinea, with the speed and confidence of something quite permanent. And on the hill, out of the alchemy of the money and the trees, four lights shone, hard against the night.